Currently, in a manufacturing process of a display apparatus (such as, TFT-LCD and AMOLED), especially in a manufacturing process of a color filter substrate, coating process is an important manufacturing process. The coating process serves a function of applying a coating material on a surface of a substrate uniformly so as to form a thin film on the surface of the substrate. Since a film thickness of the thin film will affect product quality, the manufacturing process of the display apparatus has high requirements on the film thickness of the thin film. In the coating process, uniformity of coating decides whether the coating process is good or not, and also affects the film thickness of the film.